1. Field of the Invention
This invention relates to a joint assembly for sealingly connecting the ends of a pair of sheet metal duct sections, and more particularly to a joint assembly that includes clamps for both connecting adjacent corner pieces and exerting sealing forces upon the corner pieces.
2. Description of the Prior Art
It is well known, as disclosed in U.S. Pat. Nos. 4,218,079 and 4,288,115, to connect the ends of rectangular heating and air conditioning ducts by flange portions which are secured to the duct end portions. The flange portions include a vertical or upstanding channel for receiving the right angle leg of a corner piece. A gasket is positioned between the upstanding channels of a pair of duct end portions to be connected.
Corner pieces extend into the upstanding channels to connect adjacent channels on each duct end portion. The leg portions of the flanges on the adjacent duct end portions are bolted together by bolts which extend through aligned holes of each corner piece. Nuts are tightened on the bolts to urge the legs of the corner pieces together so as to apply a compressive force upon the upstanding channels and, thereby, compress the gasket between the upstanding channels to form a seal around the adjacent duct end portions.
One disadvantage of bolting the corner pieces together to exert a sealing force on the gasket between the upstanding channels is that the clamping force generated by overtightening the bolts tends to spread apart the outer ends of the legs of the corner pieces. If the bolts are overtightened to the extent that the legs spread apart, then an ineffective seal is formed between the upstanding channels permitting air to leak around the ends of the ducts and upwardly between the connecting flanges. Furthermore, the use of nuts and bolts in assembling a duct joint is time consuming and constitutes a substantial portion of the total expense of the duct joint assembly.
Therefore, there is need for a duct joint assembly that connects the duct ends portions in a manner that eliminates the use of nuts and bolts to sealingly connect the joined duct end portions so as to reduce the material and labor costs in assembling a duct joint.